Water is the best offense. They have a short life-cycle. You must spray at least every five days to down the populations down. Secret is to spray the underside of leaves where the eggs and nymphs (or crawlers) are.

Hand held vacuum works well on adults and nymphs

Make your own pesticide

1 cup water, ¾ cup alcohol – mix and spray on plants. Always check for burning first. You can spray the solutions on and wait a few minutes for it to kill the whitefly and then spray it off with clear water as other option.